The Advanced Light Source (ALS) is a third-generation synchrotron X-ray source that operates as a user facility with more
than 40 beamlines hosting over 2000 users per year from around the world. Users of the Hard X-ray Micro-Tomography
Beamline (8.3.2) often collect more than 1 Terabyte of raw data per day that in turn generates additional Terabytes of
processed data. The data rate continues to increase rapidly due to faster detectors and new sample automation capabilities.
We will present the development and deployment of a computational pipeline, fed by data from the ALS, and powered by
the storage, networking, and computing resources of the local National Energy Research Scientific Computing Center
(NERSC) and the Energy Sciences Network (ESNET). After one year of operation, the system contained 70,000 datasets
and 350 TB of data from 85 users. All datasets now collected at the Hard X-ray Tomography Beamline are automatically
reconstructed using parameters set by users and/or that are automatically detected from the data acquisition control system.
Results are presented to users for visualization through a secure web portal. Users can then download their data or launch a
(currently limited but) growing number of operations based on the data-such as filtering, segmentation, and simulation.
The massive computational resources of NERSC are thus made available on a level that is easily accessible to the full range
of micro-tomography users.
Owing to their reduced dimensionality, the behavior of quasi-one-dimensional systems is often strongly influenced by
electron-electron interactions. We discuss some recent work on using theory and computation to understand and predict
the electronic structure and the linear optical response of several one-dimensional (1D) nanostructures. The calculations
are carried out employing a first-principles interacting-electron Green's function approach. It is shown that exciton
states in the semiconducting carbon nanotubes have binding energies that are orders of magnitude larger than bulk
semiconductors and hence they dominate the optical spectrum at all temperature, and that strongly bound excitons can
exist even in <i>metallic</i> carbon nanotubes. In addition to the optically active (bright) exciton states, theory predicts a
number of optically inactive or very weak oscillator strength (dark) exciton states. These findings demonstrate the
importance of an exciton picture in interpreting optical experiments and in the possible applications of the carbon
nanotubes. Our studies show that many-electron interaction (self-energy and excitonic) effects are equally dominant in
the electronic structure and optical response of other potentially useful quasi-1D nanostructures such as the BN
nanotubes, Si nanowires, and graphene nanoribbons.